<!DOCTYPE html>
<html lang="zh">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        html,
        body {
            margin: 0;
            padding: 0;
        }

        .grid {
            display: flex;
            justify-content: space-around;
            margin: 10px;
        }

        .grid-cell {
            padding: 20px;
            text-align: left;
            flex: 1 1 auto;
            background-color: greenyellow;
            border-radius: 10px;
            margin: 0 10px 0px 0;
        }

        .u-1,
        .u-1-1,
        .u-2-2,
        .u-3-3,
        .u-4-4,
        .u-5-5 {
            flex: 0 0 100%;
        }

        .u-1-2,
        .u-2-4 {
            flex: 0 0 50%;
        }

        .u-1-3 {
            flex: 0 0 33.33%;
        }

        .u-2-3 {
            flex: 0 0 66.66%;
        }

        .u-1-4 {
            flex: 0 0 25%;
        }

        .u-3-4 {
            flex: 0 0 75%;
        }

        .u-1-5 {
            flex: 0 0 20%;
        }

        .u-2-5 {
            flex: 0 0 40%;
        }

        .u-3-5 {
            flex: 0 0 60%;
        }

        .u-4-5 {
            flex: 0 0 80%;
        }
    </style>
</head>

<body>
    <div class="grid">
        <div class="grid-cell u-1-2">1/2</div>
        <div class="grid-cell">auto</div>
        <div class="grid-cell u-1-5">1/5</div>
    </div>
</body>

</html>